1. Field of the Invention
The invention relates in general to a touch panel and an electronic device, and more particularly to a touch panel and an electronic device for electrostatic discharge (ESD) protection.
2. Description of the Related Art
A touch screen is an electronic visual display that can detect the presence and location of a touch within the touch-sensitive area or the display area. The term of touch generally refers to touching the display of the device with a finger, or hand. Touch screens can also sense other passive objects, such as a stylus. Touch screens serve as a user interface for a number of electronic applications, such as handheld devices, or tablet computers.
The touch screen has two main attributes. First, it enables one to interact directly with what is displayed. Second, it lets one do so without requiring any intermediate device that would need to be held in the hand, such as a mouse or a physical keyboard. Such displays can be attached to computers, or to networks as terminals. They also play a prominent role in the design of digital appliances such as the personal digital assistant (PDA), satellite navigation devices, mobile phones, and video games. Touch screens are becoming increasingly popular because of their ease and versatility of operation.
There is a capacitive touch screen which includes an insulator such as glass coated with a transparent conductor such as a sensing electrode made of indium tin oxide (ITO), and a touch sensor integrated circuit (IC) operationally connected with the sensing electrode. As the human body is also an electrical conductor, touching the surface of the screen results in a change of the screen's electric field, as well as a change of capacitance on the sensing electrode. Such capacitance variance can be converted into a sensing signal. Then, the touch sensor IC can receive the sensing signal and locate where the touch is.
In view of this, the sensing electrode can behave as a touch sensor for detecting variance of electric field. However, the behavior of the sensing electrode can also be regarded as an antenna for the touch sensor IC, which could damage the sensing electrode and/or the touch sensor IC if electrostatic charge accumulates on the sensing electrode and a sudden and momentary electric current discharges or flows towards the touch sensor IC. This situation becomes worse in the case of an in-cell touch screen since the sensing electrode is inside the cell gap of the screen, and usually is floated or isolated from ground.